linux-kernel - Re: [PATCH v1 00/12] THP migration support

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Date:   Mon, 26 Sep 2016 11:38:05 -0400
From:   "Zi Yan" <zi.yan@...t.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     benh@...nel.crashing.org, mgorman@...hsingularity.net,
        kirill.shutemov@...ux.intel.com, akpm@...ux-foundation.org,
        dave.hansen@...ux.intel.com, n-horiguchi@...jp.nec.com,
        "Zi Yan" <zi.yan@...rutgers.edu>
Subject: Re: [PATCH v1 00/12] THP migration support

On 26 Sep 2016, at 11:22, zi.yan@...t.com wrote:

> From: Zi Yan <zi.yan@...rutgers.edu>
>
> Hi all,
>
> This patchset is based on Naoya Horiguchi's page migration enchancement
> for thp patchset with additional IBM ppc64 support. And I rebase it
> on the latest upstream commit.
>
> The motivation is that 4KB page migration is underutilizing the memory
> bandwidth compared to 2MB THP migration.

Sorry, in ppc64, 64KB page was used as the base page and 16MB THP
was used.

>
> As part of my internship work in NVIDIA, I compared the bandwidth
> utilizations between 512 4KB pages and 1 2MB page in both x86_64 and ppc64.
> And the results show that migrating 512 4KB pages takes only 3x and 1.15x of
> the time, compared to migrating single 2MB THP, in x86_64 and ppc64
> respectively.
>
> Here are the actual BW numbers (total_data_size/migration_time):
>         | 512 4KB pages | 1 2MB THP  |  1 4KB page
> x86_64  |  0.98GB/s     |  2.97GB/s  |   0.06GB/s
> ppc64   |  6.14GB/s     |  7.10GB/s  |   1.24GB/s

And the BW number should be:
         | 512 4KB pages | 1 2MB THP  |  1 4KB page
 x86_64  |  0.98GB/s     |  2.97GB/s  |   0.06GB/s

         | 512 64KB pages | 1 16MB THP  |  1 64KB page
 ppc64   |  6.14GB/s      |  7.10GB/s   |   1.24GB/s

>
> Any comments or advices are welcome.
>
> Here is the original message from Naoya:
>
> This patchset enhances page migration functionality to handle thp migration
> for various page migration's callers:
>  - mbind(2)
>  - move_pages(2)
>  - migrate_pages(2)
>  - cgroup/cpuset migration
>  - memory hotremove
>  - soft offline
>
> The main benefit is that we can avoid unnecessary thp splits, which helps us
> avoid performance decrease when your applications handles NUMA optimization on
> their own.
>
> The implementation is similar to that of normal page migration, the key point
> is that we modify a pmd to a pmd migration entry in swap-entry like format.
> pmd_present() is not simple and it's not enough by itself to determine whether
> a given pmd is a pmd migration entry. See patch 3/11 and 5/11 for details.
>
> Here're topics which might be helpful to start discussion:
>
> - at this point, this functionality is limited to x86_64.
>
> - there's alrealy an implementation of thp migration in autonuma code of which
>   this patchset doesn't touch anything because it works fine as it is.
>
> - fallback to thp split: current implementation just fails a migration trial if
>   thp migration fails. It's possible to retry migration after splitting the thp,
>   but that's not included in this version.
>
> Thanks,
> Zi Yan
> ---
>
> Naoya Horiguchi (11):
>   mm: mempolicy: add queue_pages_node_check()
>   mm: thp: introduce CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
>   mm: thp: add helpers related to thp/pmd migration
>   mm: thp: enable thp migration in generic path
>   mm: thp: check pmd migration entry in common path
>   mm: soft-dirty: keep soft-dirty bits over thp migration
>   mm: hwpoison: fix race between unpoisoning and freeing migrate source
>     page
>   mm: hwpoison: soft offline supports thp migration
>   mm: mempolicy: mbind and migrate_pages support thp migration
>   mm: migrate: move_pages() supports thp migration
>   mm: memory_hotplug: memory hotremove supports thp migration
>
> Zi Yan (1):
>   mm: ppc64: Add THP migration support for ppc64.
>
>  arch/powerpc/Kconfig                         |   4 +
>  arch/powerpc/include/asm/book3s/64/pgtable.h |  23 ++++
>  arch/x86/Kconfig                             |   4 +
>  arch/x86/include/asm/pgtable.h               |  28 ++++
>  arch/x86/include/asm/pgtable_64.h            |   2 +
>  arch/x86/include/asm/pgtable_types.h         |   8 +-
>  arch/x86/mm/gup.c                            |   3 +
>  fs/proc/task_mmu.c                           |  20 +--
>  include/asm-generic/pgtable.h                |  34 ++++-
>  include/linux/huge_mm.h                      |  13 ++
>  include/linux/swapops.h                      |  64 ++++++++++
>  mm/Kconfig                                   |   3 +
>  mm/gup.c                                     |   8 ++
>  mm/huge_memory.c                             | 184 +++++++++++++++++++++++++--
>  mm/memcontrol.c                              |   2 +
>  mm/memory-failure.c                          |  41 +++---
>  mm/memory.c                                  |   5 +
>  mm/memory_hotplug.c                          |   8 ++
>  mm/mempolicy.c                               | 108 ++++++++++++----
>  mm/migrate.c                                 |  49 ++++++-
>  mm/page_isolation.c                          |   9 ++
>  mm/rmap.c                                    |   5 +
>  22 files changed, 549 insertions(+), 76 deletions(-)
>
> -- 
> 2.9.3
>
> --
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--
Best Regards
Yan Zi

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